Stabilized liquid ozone



This invention relates to liquid ozone which is stable .under conditionsof rapid evaporation.

Ozone, molecular weight 48, is an unstable blue gas with a pungentcharacteristic odor and is generally encountered in dilute form inadmixture with air or oxygen. It has a melting point of 19l.l C. and aboiling point of 11l.9 C. At 1l1.9 C. ozone condensesto a dark blueliquid. Ozone is customarily handled as a gas or in admixture withliquid oxygen. It is used commercially in the purification of drinkingwater, as a powerful oxidant in both organic and inorganic reactions andin the treatment of industrial wastes. It is also used for thedeodorization of air and sewage gases as well as for the preservation offoods in cold storage. More recently, liquefied ozone has found utilityas an oxidant with rocket fuels. (See US. Patent 2,704,274 for adiscussion in some detail of this use). The handling of liquid ozoneduring its preparation, storage, shipment and use has presented newproblems since it is easily exploded as are concentrated ozone-oxygenmixtures (above about 15 weight percent ozone), in either the liquid orvapor state. These explosions may be initiated by minute amounts ofcatalysts or organic matter, shock, electric spark or sudden changes intemperature, pressure, etc. For example, any hot spots in lines, valves,etc., in a liquid ozone handling system or any leaks in such a systemcould cause rapid evaporation of the liquid ozone resulting in anexplosion.

It has now been found that liquid ozone can 'be rendered stable withrespect to initiation of an explosion under rapid evaporation conditionsby incorporating hydrochloric acid therein. The amount of hydrochloricacid added to the ozone can vary widely but generally is from about 0.5to 25 weight percent based on the ozone and preferably 0.5 to 5 weightpercent. The hydrochloric acid can be aqueous or anhydrous.

In order to evaluate the stability of the liquid ozone compositions ofthis invention a test procedure was devised whi-ch is as follows: Astandard vacuum line is used to condense, concentrate and supply ozonefor the test. A mm. pyrex tube, about 6 inches long and sealed off atthe bottom, is attached to the line after evacuation and ozone isvaporized from a storage trap and condensed into the test tube which iscooled in a liquid oxygen bath. The ozone is purified by evacuation toremove any oxygen resulting from decomposition during transfer. Afteradding nitrogen gas to the tube up to atmospheric pressure, it ismanually removed from the oxygen bath and quickly placed in a waterbath. The temperature of the latter determines the rate of boiling andis the criterion which determines effectiveness. Three types of results,upon immersion of the tube into the water bath, have been observed: anexplosion, with shattering of the tube, a vigorous boiling of the ozonefollowed by a vapor phase explosion which does not shatter the tube, ora rapid boiling with no attendant explosion. This test procedure wasemployed in the following examples:

EXAMPLE I 3 grams of ozone were condensed into the tube maintained at-183 C. by the liquid oxygen bath. The liquid ozone was purified byevacuation of the tube to remove any oxygen and the tube was pressuredto atmospheric pressure with nitrogen. The tube was manually removedfrom the liquid oxygen bath and quickly placed United States Patent 0 2in an ice-slush bath (0 C.). The tube exploded violently.

EXAMPLE II 0.08 gram of aqueous HCl (12 N) was placed in the tube andthe tube was cooled to --183 C. by immersion in a liquid oxygen bath.Ozone, 4 grams, was then condensed on top of the HCl. After the tube wasbrought to atmospheric pressure by the addition of nitrogen gas, it wasmanually removed from the oxygen bath and quickly placed in a beaker ofboiling water. Upon immersion of the tube in the boiling water, a rapidboiling of the ozone occurred with no explosion. It is apparent fromthis example that hydrochloric acid is efiective in preventing anexplosion when ozone is vigorously boiled.

The procedure of Example 11 was repeated using about 0.06 gram of water,12 N HCl, partially dehydrated 12 N HCl and anhydrous HCl (100%) as theadditive, 3 grams of ozone, and water baths maintained at0 C., 25 C., 50C., C., and C. The results are set forth in the following Table I inwhich a dash indicates no explosion, a plus sign indicates an explosionwith shattering of the tube, and 2) indicates a vigorous boilingfollowed by a vapor phase explosion which does not shatter the tube.

Table I Water bath temperature, G.

Additive Another test was devised to test the stability of the ozonecompositions of this invention. In this test 3 to 4 grams of ozone wascollected directly from an ozonizer in a trap cooled with liquid oxygen.The trap was then disconnected from the ozonizer and the ozone wasvacuum transferred to a second trap also maintained at liquid oxygentemperature which in the first two experiments was empty and in the nexttwo experiments contained a drop or two of 12 N HCl. The system was thenbrought to atmospheric pressure by back bubbling a small amount ofhelium through the ozone. The second trap was then connected to atwo-milliliter capillary tube. Then helium at approximately 30 p.s.i.g.was rapidly released into the second trap to push the ozone through thetwo-milliliter capillary tube and into the atmosphere. In the first twoexperiments wherein ozone alone was pushed into the atmosphere, animmediate explosion occurred. In the next two experiments wherein ozonecontaining the HCl was pushed into the atmosphere, no explosionoccurred.

We claim:

1. A liquid ozone composition consisting of liquid ozone and about 0.5to 25 weight percent based on the ozone of hydrochloric acid.

2. A liquid ozone composition consisting of liquid ozone and about 0.5to 5 weight percent based on the ozone of 12 Nhydrochloric acid.

7 References Cited in the file of this patent UNITED STATES PATENTS420,394 Stelzer Jan. 28, 1890 1,152,066 Wolfi Aug. 31, 1915 2,700,648Thorp et al. If an. 25, 1955 OTHER REFERENCES Thorp: Bibliography ofOzone Technology, vol. 2, pp. 30-47. John S. Swift Co., Inc., Chicago,Illinois, 1955.

1. A LIQUID OZONE COMPOSITION CONSISTING OF LIQUID OZONE AND ABOUT 0.5TO 25 WEIGHT PERCENT BASED ON THE OZONE OF HYDROCHLORIC ACID.